704 research outputs found
Baltica‐Siberia connection challenges traditional tectonics notions
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97201/1/eost10342.pd
Microbial colonization and alteration of basaltic glass
International audienceMicroorganisms have been reported to be associated with the alteration of the glassy margin of seafloor pillow basalts (Thorseth et al., 2001, 2003; Lysnes et al., 2004). The amount of iron and other biological important elements present in basalts and the vast abundance of basaltic glass in the earth's crust, make glass alteration an important process in global element cycling. To gain further insight into microbial communities associated with glass alteration, five microcosm experiments mimicking seafloor conditions were inoculated with seafloor basalt and incubated for one year. Mineral precipitations, microbial attachment to the glass and glass alteration were visualized by scanning electron microscopy (SEM), and the bacterial community composition was fingerprinted by PCR and denaturing gradient gel electrophoresis (DGGE) in combination with sequencing. SEM analysis revealed a microbial community with low morphological diversity of mainly biofilm associated and prosthecate microorganisms. Approximately 30 nm thick alteration rims developed on the glass in all microcosms after one year of incubation; this however was also seen in non inoculated controls. Calcium carbonate precipitates showed parallel, columnar and filamentous crystallization habits in the microcosms as well as in the sterile controls. DGGE analysis showed an alteration in bacterial community profiles in the five different microcosms, as a response to the different energy and redox regimes and time. In all microcosms a reduction in number of DGGE bands, in combination with an increase in cell abundance were recorded during the experiment. Sequence analysis showed that the microcosms were dominated by four groups of organisms with phylogenetic affiliation to four taxa: The Rhodospirillaceae, a family containing phototrophic marine organisms, in which some members are capable of heterotrophic growth in darkness and N2 fixation; the family Hyphomicrobiaceae, a group of prosthecate oligotrophic organisms; the genus Rhizobium, N2 fixating heterotrophs; and the genus Sphingomonas, which are known as bio-film producing oligotrophs. Although no bioalteration of glass could be confirmed from our experiments, oligotrophic surface adhering bacteria such as the Sphingomonas sp. and Hyphomicrobium sp. may nevertheless be important for bioalteration in nature, due to their firm attachment to glass surfaces, and their potential for biofilm production
The ∼270 Ma palaeolatitude of Baltica and its significance for Pangea models
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86901/1/j.1365-246X.2011.05061.x.pd
Constraining Absolute Plate Motions Since the Triassic
The absolute motion of tectonic plates since Pangea can be derived from observations of hotspot trails, paleomagnetism, or seismic tomography. However, fitting observations is typically carried out in isolation without consideration for the fit to unused data or whether the resulting plate motions are geodynamically plausible. Through the joint evaluation of global hotspot track observations (for times <80 Ma), first‐order estimates of net lithospheric rotation (NLR), and parameter estimation for paleo–trench migration (TM), we present a suite of geodynamically consistent, data‐optimized global absolute reference frames from 220 Ma to the present. Each absolute plate motion (APM) model was evaluated against six published APM models, together incorporating the full range of primary data constraints. Model performance for published and new models was quantified through a standard statistical analyses using three key diagnostic global metrics: root‐mean square plate velocities, NLR characteristics, and TM behavior. Additionally, models were assessed for consistency with published global paleomagnetic data and for ages <80 Ma for predicted relative hotspot motion, track geometry, and time dependence. Optimized APM models demonstrated significantly improved global fit with geological and geophysical observations while performing consistently with geodynamic constraints. Critically, APM models derived by limiting average rates of NLR to ~0.05°/Myr and absolute TM velocities to ~27‐mm/year fit geological observations including hotspot tracks. This suggests that this range of NLR and TM estimates may be appropriate for Earth over the last 220 Myr, providing a key step toward the practical integration of numerical geodynamics into plate tectonic reconstructions
Сучасний стан і проблеми управління залізничним транспортом України
Проаналізовано стан і тенденції розвитку залізничного транспорту. Розглянуті основні завдання державного регулювання галузі.Проанализировано состояние и тенденции развития железнодорожного транспорта. Рассмотренны основные задания государственного регулирования отрасли.The condition and trends of railway transport has been anilized. The main tasks of state regulation of railway transport has been considereted
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Volcanic constraints on the unzipping of Africa from South America: Insights from new geochronological controls along the Angola margin
The breakup of Africa from South America is associated with the emplacement of the Paraná-Etendeka flood basalt province from around 134 Ma and the Tristan da Cunha plume. Yet many additional volcanic events occur that are younger than the main pulse of the Paraná-Etendeka and straddle the rift to drift phases of the main breakup. This contribution reports on new geochronological constraints from the Angolan part of the African Margin. Three coastal and one inland section have been sampled stretching across some 400 Km, with 39Ar/40Ar, U-Pb and Palaeontology used to provide age constraints. Ages from the new data range from ~100 to 81 Ma, with three main events (cr. 100, 91 and 82-81 Ma). Volcanic events are occurring within the Early to Late Cretaceous, along this part of the margin with a general younging towards Namibia. With the constraints of additional age information both onshore and offshore Angola, a clear younging trend at the early stages of rift to drift is recorded in the volcanic events that unzip from North to South. Similar age volcanic events are reported from the Brazilian side of the conjugate margin, and highlight the need to fully incorporate these relatively low volume volcanic pulses into the plate tectonic breakup models of the South Atlantic Margin
The Cerenkov effect revisited: from swimming ducks to zero modes in gravitational analogs
We present an interdisciplinary review of the generalized Cerenkov emission
of radiation from uniformly moving sources in the different contexts of
classical electromagnetism, superfluid hydrodynamics, and classical
hydrodynamics. The details of each specific physical systems enter our theory
via the dispersion law of the excitations. A geometrical recipe to obtain the
emission patterns in both real and wavevector space from the geometrical shape
of the dispersion law is discussed and applied to a number of cases of current
experimental interest. Some consequences of these emission processes onto the
stability of condensed-matter analogs of gravitational systems are finally
illustrated.Comment: Lecture Notes at the IX SIGRAV School on "Analogue Gravity" in Como,
Italy from May 16th-21th, 201
Study protocol for a randomized controlled trial of supportive parents – coping kids (SPARCK)—a transdiagnostic and personalized parent training intervention to prevent childhood mental health problems
Background: To meet the scientific and political call for effective prevention of child and youth mental health problems and associated long-term consequences, we have co-created, tested, and optimized a transdiagnostic preventive parent-training intervention, Supportive parents – coping kids (SPARCK), together with and for the municipal preventive frontline services. The target group of SPARCK is parents of children between 4 and 12 years who display symptoms of anxiety, depression, and/or behavioral problems, that is, indicated prevention. The intervention consists of components from various empirically supported interventions representing different theorical models on parent–child interactions and child behavior and psychopathology (i.e., behavioral management interventions, attachment theory, emotion socialization theory, cognitive-behavioral therapy, and family accommodation intervention). The content and target strategies of SPARCK are tailored to the needs of the families and children, and the manual suggests how the target strategies may be personalized and combined throughout the maximum 12 sessions of the intervention. The aim of this project is to investigate the effectiveness of SPARCK on child symptoms, parenting practices, and parent and child stress hormone levels, in addition to later use of specialized services compared with usual care (UC; eg. active comparison group). Methods: We describe a randomized controlled effectiveness trial in the frontline services of child welfare, health, school health and school psychological counselling services in 24 Norwegian municipalities. It is a two-armed parallel group randomized controlled effectiveness and superiority trial with 252 families randomly allocated to SPARCK or UC. Assessment of key variables will be conducted at pre-, post-, and six-month follow-up. Discussion: The current study will contribute with knowledge on potential effects of a preventive transdiagnostic parent-training intervention when compared with UC. Our primary objective is to innovate frontline services with a usable, flexible, and effective intervention for prevention of childhood mental health problems to promote equity in access to care for families and children across a heterogeneous service landscape characterized by variations in available resources, personnel, and end user symptomatology. Trial registration: ClinicalTrials.gov ID: NTCT0580052
Structure and Evolution of Streptomyces Interaction Networks in Soil and In Silico
Soil grains harbor an astonishing diversity of Streptomyces strains producing diverse secondary metabolites. However, it is not understood how this genotypic and chemical diversity is ecologically maintained. While secondary metabolites are known to mediate signaling and warfare among strains, no systematic measurement of the resulting interaction networks has been available. We developed a high-throughput platform to measure all pairwise interactions among 64 Streptomyces strains isolated from several individual grains of soil. We acquired more than 10,000 time-lapse movies of colony development of each isolate on media containing compounds produced by each of the other isolates. We observed a rich set of such sender-receiver interactions, including inhibition and promotion of growth and aerial mycelium formation. The probability that two random isolates interact is balanced; it is neither close to zero nor one. The interactions are not random: the distribution of the number of interactions per sender is bimodal and there is enrichment for reciprocity—if strain A inhibits or promotes B, it is likely that B also inhibits or promotes A. Such reciprocity is further enriched in strains derived from the same soil grain, suggesting that it may be a property of coexisting communities. Interactions appear to evolve rapidly: isolates with identical 16S rRNA sequences can have very different interaction patterns. A simple eco-evolutionary model of bacteria interacting through antibiotic production shows how fast evolution of production and resistance can lead to the observed statistical properties of the network. In the model, communities are evolutionarily unstable—they are constantly being invaded by strains with new sets of interactions. This combination of experimental and theoretical observations suggests that diverse Streptomyces communities do not represent a stable ecological state but an intrinsically dynamic eco-evolutionary phenomenon
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